Dutch solo sailor Laura Dekker, 14, has begun her round-the-world record bid from Gibraltar, after slipping away from the media spotlight and Portuguese police.

"She left the harbour of Gibraltar," Marijke Schaaphok, whose television company Masmedia has signed an exclusive rights contract with Dekker said.

Ms Schaaphok says Ms Dekker will probably head for the Spanish Canary Islands or possibly Portugal's Madeira, depending on the wind, arriving in six or eight days.

She says Ms Dekker has finally decided to make the the southern tip of Spain the starting point for her voyage because "the Portuguese police were making problems because of her age".

She says the police had paid Ms Dekker a visit at sea while she made final tests of her boat, the red-hulled, 11.5 metre ketch Guppy, in which she had arrived from the Netherlands in the southern Portuguese port of Portimao a week ago.

The teenager's agent, Peter Klarenbeek, had said that Ms Dekker would be leaving Portimao on Saturday, but other sailors in the marina there said she and her boat had not been seen since Wednesday.

Port authorities confirmed a report by the Lusa news agency that Portuguese law does not allow a minor to sail alone.

At the end of July Ms Dekker won a 10-month court battle with Dutch child welfare authorities who had been preventing the voyage for fear it would stunt her social and emotional development.

Ms Dekker turns 17 on September 20, 2012, allowing her a little over two years to complete the trip and set a new record, during which she intends to stop at several ports along the way.

She has said her route from Portugal will take her across the Atlantic Ocean and into the Pacific via the Panama Canal.

She plans to stop at the Galapagos islands before heading to Australia, Thailand and through the pirate-infested Gulf of Aden back to Europe.

Born in New Zealand during a round-the-world sailing trip by her parents, Ms Dekker completed her first solo voyage, to the northern Netherlands, at the age of 11.